JPS612594A - Optical information-recording member - Google Patents

Abstract

PURPOSE:To enable to record and erase information with low energy, by using a thin film of a material based on a Te-TeO2 material containing a relatively large amount of Te component with at least Sb, Ge and Au incorporated therein, in which the compositional ratios of the additives are specified. CONSTITUTION:The thin film is provided in which the relative values of the total number of atoms of Te-Sb-Ge and the numbers of atoms of Au and O lie in the shaded region A-E on Fig. 7 and the relative numbers of atoms of Te, Ge and Sb lie in the shaded region F-K on Fig. 8. Accordingly, by using the thin film of the five-element oxide system Te-O-Ge-Sb-Au, an optical information-recording member can be obtained which comprises Te as a main constituent for reversible change and has a combination of excellent characteristics owing to the respective effects of the constituents, namely, enhancement of thermal stability by Ge, enhancement of recording sensitivity by Sb, enhancement of erasing speed by Au, and enhancement of moisture resistance by O.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an optical information recording member that uses a laser beam to record and reproduce information signals at high density and high speed, and that allows information to be rewritten.

Conventional configurations and their problems The technology for recording and reproducing high-density information using laser beams is already well known, and is currently being actively applied to document file systems, still image file systems, etc. Furthermore, research and development cases are being reported regarding rewritable recording systems.

Regarding recording media in which information is repeatedly recorded and erased by reversibly increasing or decreasing the optical properties of the recording thin film, such as the refractive index and extinction coefficient, using a laser beam, for example, Japanese Patent Publication No. 47
T @ s , G e 1s found in -26897
Amorphous thin films based on chalcogen elements other than oxygen, such as S b 2 S 2 , have been known, but they have not been put into practical use due to the problem of being sensitive to moisture. An oxide-based thin film based on Te and O has improved moisture resistance. These erase records by irradiating relatively strong and short pulsed light to rapidly cool the irradiated area from a heated state to decrease its optical constant, and by irradiating relatively weak and long pulsed light to increase the optical constant. The idea is to generally use the direction in which the optical constant decreases during recording and the direction in which it increases during erasing.

A Te-Tea2 thin film, which has been conventionally used as a recording material, is produced in a state in which small particles of Te (~20 particles) are scattered in an amorphous TeO2 matrix, or in a state in which Te and TeO2 are separated by, for example, X-ray radiation. It is thought that the Te particles are mixed in an almost amorphous state with no peak detected in the analysis, but in any case, it is the Te particles that change their structure significantly upon irradiation with light and contribute to the recording of information signals. Therefore, by combining these Te particles with an appropriate substance, the thermal conditions necessary for reversible structural changes of Te can be controlled, and for example, the irradiation power and irradiation time required for erasing records with laser beams can be controlled to some extent. is possible.

For example, Japanese Patent Application Laid-Open No. 55-28530 describes a method for increasing the reversibility of structural changes in Te-Tea2 thin films using Ss and S, and Japanese Patent Application No. 58-68158 describes a method for increasing the reversibility of structural changes in Te-Tea2 thin films using Ss and S. There is a proposal for a method of increasing the structural reversibility of the Te-Teo2 thin film by adding elements such as , Sb, and Bi, and at the same time improving the stability of the film and the reproducibility during manufacturing. Subsequent detailed research revealed that, for example, when Ge is added, the Te particle size increases and the energy required to restore order increases rapidly, making it possible to control the thermal stability of recorded signal bits even in small amounts (1983 , Proceedings of the 30th Applied Physics Conference, P87~), and due to its semimetallic properties, when Sn solidifies from a molten state due to laser beam irradiation during recording, it combines with Te and slows down the grain size growth. It has become clear that in addition to the suppressing effect, G
An optical disk was prototyped using a recording thin film to which e and Sn were simultaneously added (1983 JAPAN DISPL
AY Proceedings P46~). This disc records simultaneously in real time.

Although it had the excellent characteristics of being able to erase data and stably recording signal bits, the sensitivity, especially the erasing sensitivity, was not sufficient. , further improvement in sensitivity was required.

OBJECTS OF THE INVENTION The object of the present invention is to improve the conventional Te TeO2 oxide thin film and provide a highly sensitive one-degree optical information recording medium that can record and erase with low power.

Structure of the Invention In order to achieve the above object, the present invention includes at least Sb, Sb,
A thin film made by adding Ge and Au at the same time is used, and by appropriately selecting the composition ratio of each of the additives, it is possible to improve the recording/erasing sensitivity without impairing the stability of the recording thin film.

DESCRIPTION OF EMBODIMENTS The present invention will now be described in detail with reference to the drawings. Figure 1 shows
FIG. 1 is a sectional view of an optical information recording member of the present invention. In the present invention, the recording thin film 2 is formed on the base material 1 by a method such as vapor deposition or sputtering. The base material may be one used for ordinary optical discs (PMMA, vinyl chloride,
Transparent resin such as polycarbonate, a glass plate, etc. can be used.

As the recording thin film, a 6-element thin film is used, which is made by adding Au to the quaternary Te-0-Sb-Go. As mentioned above, a recording thin film formed using a quaternary thin film of Te-0-8n-Ge is capable of recording and erasing data simultaneously in real time, but the sensitivity is not sufficient.

The sensitivity limit in the Te-0-3n-Ge four-element system is thought to be due to the fact that Sn serves two functions as described above. In other words, by changing the additive concentration of Sn, for example, if the additive concentration of Sn is increased, the effect as a nucleus for recovering crystallinity, which is one of the two functions, becomes greater, but on the other hand, the melting point of the entire system increases. It becomes difficult to melt, making it difficult to record. On the other hand, when it decreases, the melting point decreases and it becomes easier to melt, but on the other hand, the number of crystal nuclei during erasing decreases and it becomes difficult to erase. Of course, if the amount decreases extremely, the effect of suppressing Te grain size growth will be lost and reversibility will be lost. In other words, recording sensitivity and erasing sensitivity both depend on the Sn concentration at the same time, so in an actual system, it is impossible to select a concentration that satisfies both of them, and this creates a compositional sensitivity limit. be.

Therefore, in the present invention, the role of the above an is divided into two,
O8b aims to expand the degree of freedom in material design and further improve sensitivity by separately combining the role of Te to suppress grain growth during recording with Bi and the role of nucleation during erasing with Au. Because of its semimetallic properties, like Sn, it tends to combine with Te in the film to form an amorphous state, and for example, a compound with Te, Sb2Te3,
It has a lower melting point than e, and can be expected to improve recording sensitivity. The effect of adding Au to a TeTeO2 thin film has already been clarified in Japanese Patent Application No. 59-61463. In other words, Au is Au-T in the TeTeO2 thin film.
It forms some kind of compound called e, which easily crystallizes, so it acts as a crystal nucleus during erasure and increases the erasure sensitivity.In addition, since the nature of Au is that it is resistant to oxidation, even a small amount of addition is sufficient to improve the overall system. It has little effect on other properties. Furthermore, in the system to which Au is added, the melting point is lowered, and it is thought that the recording characteristics can be improved by combining it with other additives.

In the present invention, Te-Tea2-based materials are used. As mentioned above, Ge is used as a thermal stability control element, Sb is used as a recording property control element, and Au is used as an erasure property control element, and the composition ratio of each element is changed to create an optimal composition. was extracted.

The present invention will be explained in more detail below using specific examples.
First, a method for manufacturing the Te-0-Go-Sb-Au recording material of the present invention will be explained.

FIG. 2 shows the inside of a Pelger of a quaternary vapor deposition apparatus used for manufacturing the recording member of the present invention. In the figure, 1
4 to 17 are Te TeO2゜Ge, Sb, Au, respectively
Sources corresponding to 10 to 13 are shutters, 6
9 shows the head of the film thickness monitoring device. After drawing the vacuum system 1B to a vacuum of about 0-5 Terr, using four electron beam guns (not shown) provided in the vacuum system,
Each of the four sources is separately heated with an electron beam, the evaporation rate is monitored, and the T e -0- A 6-element thin film of Ge-8b-Au is synthesized.

At this time, for example, the Te-Te02 source is
The sintered pellets described in 8-116317 can be used, and it is possible to precisely control the six elements using four sources. The film composition is AES.

It can be determined using methods such as XPS, XMA, SIMS, etc.

Of course, it is possible to use six sources as the vapor deposition method, and it is also possible to reduce the number of sources by using the mixture pellets described in Japanese Patent Application No. 68-233009. Furthermore, it is also possible to form by sputtering.

Next, a method for evaluating the characteristics of the recording thin film formed by the above method will be described.

Since the recording member of the present invention utilizes repeated and reversible changes, it has a characteristic in the direction in which the optical constant increases (called blackening because the optical density increases), that is, an erasing characteristic, and a characteristic in the direction in which the optical constant decreases (optical density In other words, it is necessary to evaluate the recording characteristics at the same time.

FIG. 3 simply shows an evaluation system for the recording member of the present invention. The light emitted from the semiconductor laser 19 is collimated by the first lens 20, then shaped into a circular beam by the second lens system 21, and then passed through the beam splitter 22 and the λ/4 plate 2.
The sheet metal 3 is focused by the third lens 24 into a circular spot of approximately 0.9 μm at half maximum, and is irradiated onto the recording medium 26 .

The reflected light follows a path opposite to that of the incident light, is bent by a beam splitter 22, is converged by a fourth lens 27, and enters a photodetector 28 to confirm the recording state.

In the present invention, the semiconductor laser is modulated, and the irradiation power is set to a relatively small value, for example, 1 mW/μ, for evaluating the blackening characteristics.
Fix the power density to about m2 and change the irradiation time and measure the irradiation time at which blackening starts, or set the irradiation time to 1μ, for example.
A method such as fixing the irradiation light to the crown level and changing the irradiation light power to measure the irradiation light power at which blackening begins is applied. Similarly, to evaluate the whitening characteristics, the recording member is blackened in advance, the irradiation light power is fixed at a relatively high level, for example, 7 mW/μ-, and the shortest irradiation time required for whitening is measured, or the irradiation time is set to 5QnlE, for example. A method such as fixing the level and changing the irradiation light power and measuring the irradiation light power at which whitening starts is applied.

Next, the results of evaluating recording members of various compositions formed by the above-described method using the above-described method will be described.

Example 1 As the evaluation material composition, the composition was controlled so that the ratio of the number of atoms of Te-Ge-Sb was 76:10:15, and at the same time, this T @ 7s G lil 1o S b 1
The compositions of Au and O were controlled as three systems: es, Au, and 0, and recording members with various compositions were obtained.

Figure 4a shows (TeO, 75GeO, 1”
bo, 16) 80o20:) Mari, T @ e
This figure shows the change in the irradiation time required to start blackening when oG @ s S b 12020 is irradiated with a power of 1 mW/μm 2 with different amounts of Au added. From this figure, it can be seen that the addition of Au greatly shortens the irradiation time to start blackening, but a sufficient effect can already be obtained with an addition amount of about 2%. b is, for example, 1 mW
The graph shows the change in the irradiation power required to start whitening when the irradiation time is 60 n SIK and the irradiation power is varied to irradiate a blackened area by irradiation with a power of /μ- for 6 μm. From this, it can be seen that although adding Au increases the irradiation light power required to start whitening, there is no practical problem up to about 16 inches, and that whitening is extremely difficult to occur at 20 inches. From these two figures, Te-0-Sb-Go
- The basic characteristics can be secured in the Au system, and by selecting the amount of Au added in the range of 2 to 15%, the recording characteristics will not be impaired (it is possible to erase at several times the speed of conventional methods) I understand. At this time, it was confirmed that each curve shifted to the left when the irradiation power density was increased.

Next, the results of similar experiments conducted on systems in which the composition ratio of Te-GeSb was changed will be explained.

Example 2 Evaluation material composition: Te-Ge-5b, Au, O
The composition was controlled so that the composition ratio was 70:10:20, and recording members with various compositions were obtained by changing the composition ratio of the three components Te-Go-Sb.

Figure 6a shows that 3 of Te-Sb-Go in the above composition.
For example, when the composition ratio of Sb in the component system is set to 20% and the composition ratio of Ge is changed, the blackening start temperature is calculated from JP-A-59-7.
The results of the investigation using the method described in 0229 are shown below. From this figure, it can be seen that as the concentration of Go added increases, the blackening initiation temperature increases and the thermal stability of the white state increases. When these recording films were left in a clean open at 50°C and their transmittance changes were examined, it was confirmed that the transmittance decreased after about 24 hours for those whose change start temperature was 100°C or lower.
If it is more than that, only a change of about 1% in absolute amount is observed even after about one month, and it is considered that thermal stability is sufficient if the Go concentration is 3% or more. If the Go concentration is further increased, the film will be able to withstand higher temperature conditions, but the film's transmittance will greatly increase (absorption will decrease), and the blackening sensitivity will tend to decrease. Go addition concentration is 3%~
Sufficient erasing sensitivity was obtained in the range of 16 inches.

Figure 6 shows Go occupying in the Te-5b-Ge three-component system.
This shows the change in recording sensitivity when the composition ratio of Sb is changed to 10%.During the irradiation pulse, approximately 50 nS
It is eC. This figure shows that when the concentration of Sb added is about 6%, the sensitivity is slightly poor and the amount of change in reflectance is small, and when it is less than that, it is difficult to whiten, and when the concentration is about 1° and 3°, sufficient recording (whitening) sensitivity can be obtained. It can be seen that when it reaches about 36%, the sensitivity decreases a little and the amount of change in reflectance decreases.

At this time, it was found that the erasing speed was several times higher than that of the conventional method due to the effect of Au. If the Sb concentration is further increased, the proportion of Te, which is the main component, will eventually decrease and the reversibility itself will be lost.

As described above, the appropriate concentration of each component was found.

Next, the results of comparing the durability against humidity of the thin films of the present invention will be shown.

Example 3 It has been known that the moisture resistance of oxide thin films based on T e "T e O□ system changes depending on the oxygen concentration in the film.
Based on the composition of e7°G e s S b 1s A u 1°, the composition was controlled so that the oxygen concentration varied within the range of 0 to 60%.

FIG. 6 shows the results of examining the change in transmittance when the thin film was left in a constant temperature and humidity chamber at 40'C and 90RH% for about one month. This figure shows that if the composition ratio of oxygen in the entire system is 10% or more, there is a decrease in transmittance at the initial stage, but there is almost no change after that, and if it is 30% or more, there is no change from the initial state. It can be seen that no change is observed.

Oxygen combines with Te in the film to form T e O2, or with Ge and Sb to form G e O
2.

5b2Q3, etc. or a composite oxide of these may be formed, but in both cases Te
It is thought that by intermixing the Te-based alloy in a divided manner, it works to improve its moisture resistance. However, if the O component is increased too much, the heat transfer coefficient of the system decreases and heat due to light irradiation tends to be accumulated, and as a result, the film becomes more likely to break during repeated cycles. 0 component is 40%
It turns out that there is no problem with this point if the following is true.

To summarize the above evaluation results, T o −〇 −G e
-5b-Au five-element thin film has a composition ratio of the three components Te-Ge-8b belonging to the region surrounded by F to K in Fig. 8, and a composition ratio of Te, Go, Sb, Au, and O. is the seventh
In the area surrounded by A to E in the figure, for example, T @
aoo 20G Q es S b 1o A u s
It was found that those represented by the following have excellent recording/erasing characteristics and recording characteristics with excellent stability. The coordinates of each point are shown in the table below.

Effect of the invention According to the present invention, T e -0-G e -8b -A
Using a 5-element oxide thin film of
To obtain an optical information recording member with excellent characteristics that combines the following effects: 2) improvement in thermal stability by Sb, 3) improvement in erasing speed by Au, and 4) improvement in moisture resistance by O. I can do it.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an embodiment of the optical information recording member of the present invention, and FIG. 2 is a partially cutaway perspective view showing the configuration of an example of a vapor deposition apparatus for manufacturing the optical information recording medium of the present invention. FIG. 3 is a cross-sectional view showing an optical system of an apparatus for measuring the recording and erasing characteristics of the optical information recording member of the present invention, and FIG. Graph showing changes, Figure 6(a)', (
b) is a graph showing Go concentration, blackening start temperature, and Sb concentration and whitening start power characteristics of the optical information recording member of the present invention, and FIG. 6 is a graph showing 0 concentration and moisture resistance characteristics in an example of the present invention. 7 and 8 are triangular diagrams showing the composition range of the optical information recording film used in the optical information recording member of the present invention. 1... Base material, 2... Recording thin film. Name of agent: Patent attorney Toshi Isamu Nakao and 1 other person 1st
Figure 2 Figure 3 Figure 4 (antt) "Y ray 1" 7- (yPIw/) (, -) 5th
Figure (Q> (A) Figure 6 Purchase time (〆ay) Figure 7/ρρ γe- to e-θb

Claims (1)

[Claims] In a thin film consisting of at least Te, O, Sb, Ge, and Au, the ratio of the sum of the number of Te-Sb-Ge atoms to the number of Au and O atoms in the film is surrounded by A to E in Figure 7. 8. An optical information recording member comprising a thin film which is present in the diagonally shaded region and whose ratio of the number of atoms of Te, Ge, and Sb is present in the region surrounded by F to K in FIG.